The ultimate goal of this project is to better understand the molecular basis for the propensity of group A streptococci to cause human disease, the role of complement chemotaxins in leukocyte aggregation associated with vascular and pulmonary pathology, and chemotaxin mediated inflammatory disease. This research is focused on our discovery that virulent group A streptococci produced a potent inactivator, designated SCFI, of human serum derived, leukocyte responsive chemotaxins. This inactivator will be isolated from a high producing strain of streptococcus, purified by various column chromatographic procedures, and chemically difined with respect to known streptococcal surface components. Finally, these studies will be extended to animal models. The immunity of SCFI and its relationship to streptococcal virulence will be assessed in rabbits and mice, respectively. The potential of SCFI administered to rabbits to inhibit the migration in response to C5a will be tested. Leukocyte aggregation will be monitored by aggregometry. The dermal arthus reaction in rabbits will be used to examine possible anti-inflammatory properties of this streptococcal product.